The present invention relates to a vehicle seat recliner for supporting and reclining a seat back of a vehicle seat with respect to a seat base of the vehicle seat.
Japanese Patent Application Publication No. 2010-253101 (JP 2010-253101 A) discloses a vehicle seat recliner for reclining a seat back with respect to a seat base. The vehicle seat recliner includes: an external gear configured to be fixed to a first one of a frame of the seat base and a frame of the seat back, wherein the external gear includes external gear teeth at its outer periphery; an internal gear configured to be fixed to a second one of the frame of the seat base and the frame of the seat back, wherein the internal gear includes internal gear teeth, and wherein the internal gear teeth are larger in tooth number than the external gear teeth of the external gear, and are in mesh with the external gear teeth of the external gear; and a rotation shaft supported rotatably in a central portion of the external gear, and configured to be rotated to cause relative revolution and relative rotation between the internal gear and the external gear. A cover is placed to cover the internal gear, and fixed to the second frame. Namely, the second frame is layered on the cover that is layered on the internal gear. In other words, the cover is disposed between the internal gear and the second frame. The components other than the frame of the seat base and the frame of the seat back are integrated as a unit of joint, and this unit of joint is disposed between the frame of the seat base and the frame of the seat back.